The enzymatic degradation of polysaccharides to monosaccharides is an essential step in bioconversion processes of lignocellulosic materials. Alkali treated brewers spent grain was used as a model substrate for the study of cellulose and hemicellulose hydrolysis by Fusarium oxysporum enzyme extract. The results obtained showed that cellulose and hemicellulose conversions are not affected by the same factors, implementing different strategies for a successful bioconversion. Satisfactory cellulose conversion could be achieved by increasing the enzyme dosage in order to overcome the end-product inhibition, while the complexity of hemicellulose structure imposes the presence of specific enzyme activities in the enzyme mixture used. All the factors investigated were combined in a mathematical model describing and predicting alkali treated brewers spent grain conversion by F. oxysporum enzyme extract.
[Show abstract][Hide abstract] ABSTRACT: a b s t r a c t Consolidated BioProcessing (CBP) can provide an important contribution to reducing ethanol production costs and moving from cellulosic feedstock to fuel ethanol tanks. Several efforts have so far been focused mainly on CBP category II engineering an ethanologen yeast or bacterium to be cellulolytic, but the limited ability of the category II CBP system for producing enzymes for lignocellulose degradation remains a challenge. As an alternative, category I CBP, aimed at engineering a cellulase producer to be ethanologenic, could be pursued, but it is still in its infancy. Some cellulolytic thermophilic bacteria have been described as potential candidates for category I CBP. However, only fungi naturally produce the needed titers of cellulases required for the complete saccharification of pretreated lignocellulose. In this review, potential of cellulolytic fungi as candidates for category I CBP is discussed.
Renewable and Sustainable Energy Reviews 02/2012; 16(5):3286-3301. DOI:10.1016/j.rser.2012.02.050 · 5.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: The high crystallinity of cellulose underlies the recalcitrance that this polymer presents in enzymatic degradation. Thus, a pre-treatment step is applied in most bioconversion processes. Treatments with ionic liquids are considered an emerging pre-treatment technology, owing to their high efficiency in solvating cellulose, over molecular solvent systems.
RESULTS: Crystalline cellulose with and without ionic liquid( 1-ethyl-3-methylimidazoliumacetate) treatment, bothcommercially available, were used as substrates in enzymatic hydrolysis reactions using the earlier evaluated cellulolytic system of Fusarium oxysporum. The in situ removal of the hydrolysate during reactions enhanced the reaction rate as well as the overall glucose production. Ionic liquid treatment significantly decreased cellulose crystallinity and enhanced bioconversion yields and rates. The effects of cellulose structural changes during treatmentonhydrolysis rate were investigated andthe recalcitrance constants were determined.
CONCLUSION: The study showed that ionic liquid-treated cellulose became more homogeneous and more easily degradable than the untreated cellulose, a conclusion that was expressed mathematically by the difference in the recalcitrance constants for the two substrates. It was concluded that glucose production from ionic liquid-treated cellulose could achieve very high conversion yields in consolidated bioprocesses or during simultaneous saccharification and fermentation. (C) 2012 Society of Chemical Industry
Journal of Chemical Technology & Biotechnology 05/2012; 87(5-5):629-634. DOI:10.1002/Jctb.2756 · 2.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose
Brewers spent grain (BSG) is a by-product of the brewing process corresponding to around 85% of total by-products generated. The great number of publications over the last 5 years, on the biotechnological applications of BSG, represents the increased scientific interest on it. This critical, state of the art review aims at gathering and analysing the most recent scientific efforts on the biotechnological potential of Brewer’s spent grain and on its evaluation as a feedstock for high added value products.
The assiduous bibliographic retrospection focused on the latest scientific reports. The consideration of all relevant scientific articles was thorough and critical. The classification of the scientific efforts was made not only according to the end-products but also according to the biotechnological approach adopted.
BSG has been used in a wide range of biotechnological applications such as substrate for enzymes production, as a source for value-added products (antioxidants, monosaccharides, oligosaccharides, xylitol, arabitol, bioethanol, biogas or lactic acid) or for the production of functional proteins and lipids. Its applications as a carrier in various bioprocesses have also been reported.
The implementation of BSG’s fractionation in industrial scale seems to be the next step in BSG’s exploitation. A fractionation process which allows the exploitation of biomolecules belonging to different classes, produced from one feedstock (BSG) may be used as a pattern for the implementation of the biorefinery concept in industrial scale, as long as the methods adopted ensure the functionality of the potentially valuable components.
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